I am building a project that will have about 25 max 7219s on separate boards.· Each board will also contain an 8 by 8 led display that the max 7219 will control.· I want to connect all of those 7219s so I can send signals to change the lights.

What's the best way to connect them?· I believe there will be five wires going from one board to the next.· I don't want to solder the wires to the boards so I'd like something that I can plug in and pull out.· The boards will be pretty close to each other, less than 6 inches on the average.

thanks

bob

Philip Gamblin

08-11-2005, 11:52 AM

For five low current control signals, I would use ribbon cable and header strips. That way you can simply press the connectors on.
However the conductors are too small to carry any significant current.

Yanroy

08-11-2005, 10:27 PM

I'm a huge fan of the Molex KK series connectors.· I use them all the time (as well as the larger molex connectors).· These things look similar to the breakaway headers you'll find on the OEM stamp modules, but they're positive-locking and polarized.

bobroan

08-13-2005, 07:02 AM

Yanroy, where do you get your·molex connectors?

Phillip, I like the ribbon cables, but didn't think the headers came with less than 10 connectors.· And do you know how I can figure out how much current they can carry?

thanks to both of you

bob

OakGraphics

08-14-2005, 01:30 AM

bobroan said...

Yanroy, where do you get your·molex connectors?

bob

Try digikey· http://www.digikey.com

lots of fun things.

I use EH series 2.5mm connectors personally - check them out at

http://dkc3.digikey.com/PDF/T052/0083.pdf

They are rated at 3A AC, DC (AWG 22) at 250V AC, DC - so pretty darn good.· What I like about them is they are really positivly connected (i.e. they will not wiggle out and need some force to remove) as well as polarized connectors (so no guessing which way they go).

If you wanted higher current - I would suggest going to the 0.156"· as they are rated up to 7 Amps (w/18 AWG wire)· You can check them out at http://dkc3.digikey.com/PDF/T052/0093.pdf

hope this helps,

Daniel

OakGraphics

08-14-2005, 02:49 AM

Oh yeah - forgot to ask - are you daisy-chaining the 7219 chips?· if that's the case you may need 6 pins:
Pin1: VCC
Pin2: VSS
Pin3: DIN
Pin4: CLK
Pin5: LOAD
Pin6: DOUT (to next 7219 DIN)
You would need to peel out pin 6 to pin 3 of the next cable, and daisy-chain the rest of the pins as well.
I would probably - for simple wiring, make 2 headers on each remote board with 5 pins each, one header for 'incoming' and the next header for 'outgoing' to the next board in the loop.
Then it would be:
Header 1: (incoming)
Pin1: VCC
Pin2: VSS
Pin3: DIN
Pin4: CLK
Pin5: LOAD
Header 2: (outgoing)
Pin1: VCC
Pin2: VSS
Pin3: DOUT
Pin4: CLK
Pin5: LOAD
If you are worried about power consumption, you could always split out the power to a 2-pin header on each remote board using the suggested 0.156" headers - and then just use 3-pin 25mm (0.1") headers for the 'data' portion:· :-)
Then it would be:
Header 1: (incoming) (0.1" header)
Pin1: DIN
Pin2: CLK
Pin3: LOAD
Header 2: (outgoing) (0.1" header)
Pin1: DOUT
Pin2: CLK
Pin3: LOAD
Header 3: (PWR) (0.156" header)
Pin1: VSS
Pin2: VCC

OakGraphics

08-14-2005, 03:36 AM

Oh - just re-read the post - you are using an 8x8 matrix. :-)

So here is what I think what the connections and circuit·would look like (assuming you are letting the 7219 control the brightness - and only 1 led per leg

Also - fantastic source of info on the 7219 http://pdfserv.maxim-ic.com/en/ds/MAX7219-MAX7221.pdf· - expecially if you are going to gang together a ton of leds per leg, it has a circuit design in it to incorporate higher current draw using a max394 analog switch, but you could do the same thing with a uln2803 per 8 led clusters·( http://www.rentron.com/Files/uln2803.pdf·)

Funny how lots of us are on the same idea lately.

knightofoldcode

08-14-2005, 08:33 AM

bobroan said...
Yanroy, where do you get your molex connectors?

Phillip, I like the ribbon cables, but didn't think the headers came with less than 10 connectors. And do you know how I can figure out how much current they can carry?

thanks to both of you

bob

They can come in any size. To a limit. I know for a fact they come in 1, 2, 3, 4, 5, 6, 8, 10, etc. However, they only are rated for 1 amp connections.

I'd suggest the Molex KK connectors, as previously suggested. I've orderd myself a set of 10 each of sizes, 1 - 10, and so far I'm really impressed. They have a good hold, yet they are really convinient to use. I used to use the screw terminals, but recently switched. (Screw terminals can be had locally, Molex KK series can't.) Molex KK are rated for either 4 amp, or 2.5 Amp, just use different material pins for different ratings.